The present invention relates to novel thermographic recording compositions, as well as the thermographic recording supports obtained from these compositions. The invention is characterised by the use of saccharin derivatives (or benzoic sulfimide, or 2,3-dihydro 1,2-benz 3-isothiazolone 1,1-dioxide) of the formula: ##STR2## the one or more substituents R of the benzene portion, which are identical or different with 0.ltoreq.n.ltoreq.4 may be the following: H, alkyl, NO.sub.2, halogen, aryl, NH.sub.2, OH, COOH, SO.sub.3 H, NR.sub.1 R.sub.2, COOR.sub.3, OR.sub.4 (R.sub.1, R.sub.2, R.sub.3, R.sub.4 =alkyl or aryl, X representing H or a group possessing a labile H and capable of forming a stable anion by loss of a proton H.sup.+, and M.sup.+ representing a metal cation), or their mixtures, as color developer in thermoreactive compositions comprising a color generator compound. Preferably, X represents H, --OH, (CH.sub.2).sub.m --OH, with 1.ltoreq.m.ltoreq.10, or: ##STR3## the hydrogen atom being particularly preferred. On a rise in temperature, these derivatives of saccharin or their salts react with the color generator to give an irreversible color. These two types of products are conditioned on a support (paper or other) which may be used in all equipment having a thermal visualisation system for data: for example, computer printers, medical and industrial monitoring equipment, telecopiers.
At present, the industrial uses of saccharin and its derivatives are as follows.
Sweetening agent: in fact, on account of its intense sweet taste, saccharin finds its principal use here.
Complexing agent for metallic silver formed by reduction in a photothermographic system, enabling the colors to be intensified. FUJI PHOTO FILM Co., FR No. 1 542 505, Oct. 18, 1968, 3M, U.S. Pat. No. 3,080,254 (Mar. 5, 1963). 1963). In this U.S. Pat. No. 3,080,254, the use of certain heterocyclic derivatives among which is saccharin, are recommended to form complexes in ionic form with silver ions.
In the present application saccharin is used in another form and in the presence of dyes to react with the latter.
Bactericidal and fungicidal agent: this is the case of certain derivatives of suitably substituted saccharin.
JAPAN AGRICULTURAL CHEMICALS AND INSECTICIDES Co. Ltd, PA0 MEIJI SEIKA KAISHA LTD, Japan Kokai, PA0 KUMIAI CHEMICAL INDUSTRI Co. Ltd, PA0 DYNAMIT NOBEL A.G., Ger. offen. No. 2,800,019, Jan. 2, 1978, PA0 CIBA GEIGY A.G., PA0 NATIONAL STARCH AND CHEMICAL CORP., Ger. Offen No. 2,805,174, Feb. 1, 1979 and U.S. Pat. No. 4,052,244, Oct. 4, 1977. PA0 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophtalide (CVL), 3,3-bis-(p-dimethylaminophenyl)phtalide , 3-(p-dimethylaminophenyl)-3-(1,2-dimethylindole-3-yl)phtalide, 3-(p-dimethylaminophenyl)-3-(2-methylindole-3-yl)phtalide, 3,3-bis-(1,2-dimethylindole-3-yl)-5-dimethylaminophtalide, 3,3-bis-(1,2-dimethylindole-3-yl)-6-dimethylaminophtalide, 3,3-bis-(9-ethylcarbazole-3-yl)-5-dimethylaminophtalide, 3,3-bis(2-phenylindole-3-yl)-5-dimethylaminophtalide, 3-p-dimethylminophenyl-3-(1-methylpyrrole-2-yl)-6-dimethylaminophtalide, ether benzylique de 4,4'-bis-dimethylaminobenshydrine, N-halogenophenyl-leuco-auramine, N-2,4,5-trichlorophenyl-leuco-auramine, rhodamine-B-anilinolactame, rhodamine-(p-nitro-anilino)lactame, rhodamine-(p-chloranilino)lactame, 7-dimethylamino-2-methoxyfluorane, 7-diethylamino-2-methoxyfluorane, 7-diethylamino-3-methoxyfluorane, 7-diethylamino-3-chlorofluorane, 7-diethylamino-3-chloro-2-methylfluorane, 7-diethylamino-2, 3-dimethylfluorane, 7-diethylamino-(3-acetylmethylamino)fluorane, 7-diethylamino-(3-methylamino)fluorane, 3,7-diethylaminofluorane, 7-diethylamino-3-(dibenzylamino)fluorane, 7-diethylamino-3-(methylbenzylamino)fluorane, 7-diethylamino-3-(chlorethylmethyl-amino)fluorane, 7-diethylamino-3-(diathylamino)fluorane, 2-phenylamino-3-methyl-6-(N-ethyl-N-p-toluyl)amino-fluorane, bleu de benzoyl-leucomethylene, bleu de p-nitrobenzyl-leucomethylene, 3-methyl-spiro-dinaphtopyrane, 3-ethyl-spiro-dinaphtopyrane, 3,3'-dichloro-spiro-dinaphtopyrane, 3-benzyl-spiro-dinaphtopyrane, 3-methyl-naphto-(3-methoxybenzo)-spiro-pyrane et 3-propyl-spiro-dibenzopyrane.
Japan No. 72 46,059 (Nov. 20, 1972), PA1 Tokkyo Koho No. 79,109,968 (Aug. 29, 1979), No. 79,109,986 (Aug. 29, 1979), PA1 Japan No. 73,05,906 (Feb. 21, 1973), PA1 Japan No. 73,08,500 (Mar. 15, 1973), PA1 Japan Kokai No. 73,08,929 (Feb. 3, 1973). PA1 Ger. Offan No. 2,727,699, Jan. 5, 1978, PA1 Ger. Offan No. 2,727,775, Jan. 5, 1978.
Combustion retarding and fire-extinguishing agent:
Adhesive cross-linking catalyst:
All these uses have nothing to do with the use according to the present invention: developer of color generators in thermoreactive compositions.
The recent increase in requirements in information and in communication has caused the use and demand for recording systems to progress, in the transmission and restitution of data. Among the latter, thermoreactive systems have experienced a very considerable development and this for several reasons:
the process of formation of the image is simple and enables good quality reproductions to be obtained as regards color and contrast,
the equipment used is often easy to maintain and use,
the thermal recording sheet, in addition to its remarkable technical performance, is of relatively low cost.
As recording sheets sensitive to heat usable for these applications, are known those described initially in French patent No. 1 440 892 (NATIONAL CASH REGISTER COMPANY) and subsequently, in the cascade of patents derived from this principal system, thus for example the patents U.S. Pat. No. 3,539,375 (NCR Company) and U.S. Pat. No. 3,746,675 (NCR Company).
All these patents deal with the following system: the heating induced is the reaction in the molten state of a colorless or pale colored chromogenic leuco-dye (color generator) and of a phenolic substance (developer) and leads to the formation of a colored species.
Different leuco-dye-phenolic compound couples have been described for these thermographic applications. For the first may be mentioned: the indolinic spiropyrans, the triphenyl-methane dye lactones, compounds of the family of fluoranes, phthalides, spirodihydropyrans (French Pat. No. 2 272 082), chromenes or chromanes, etc. For the second, may be mentioned: bisphenol A (4,4'-isopropylidene diphenol), p-tertiobutylphenol, p-phenylphenol, p,p'(methyl-1-n-hexylidene)diphenol, phenolic novolac resine resins etc.
Also known, as thermoreactive recording compositions, are those containing other developers of the above-described leuco-dyes, in place of phenolic comounds, such as for example:
metal salts of organic acid and, preferably, fatty acids, (resinates, acetates, phenates, stearates, ricinoleates, oleates, etc.). Swiss Pat. No. 406 257 (NCR Company),
compounds of the structure: ##STR4##
French patent application No. 79 28 857 (CIBA-GEIGY A.G.),
carbonate or ether derivatives of 2,3-dihydroxy naphthalene. French patent application No. 2 427 210 (78-16 954) (LA CELLOPHANE),
siliceous and phosphorus derivatives of 2,3-dihydroxy naphthalene. French patent application No. 2 427 209 (78-16 953) (LA CELLOPHANE),
electronegatively substituted monoaldehydes or polyaldehydes and/or their reaction products with an organic compound containing hydroxyl groups or the intermediate products. Patent application in FRANCE No. 2 391 858 (78-15 806) (CIBA-GEIGY A.G.).
All these processes have, of course, their own qualities. It remains nonetheless that they have for the most part imperfections, particularly, as regards the stability and persistance over the long term of the recorded image. In fact, the majority of the latter have a more or less marked fading of the recorded colorations under the effect of ambient light, as well as an increase in the background fog in humidity and in heat.
This stability of the recorded image and of the uncolored background depends, quite obviously, on the nature and the structure of the leuco-dye colour generator used, but also on the developer selected in combination with it. The combination chosen between the dye precursor and the developer has hence great importance on the qualities of preservation of the paper and of the recorded image.